title: Influence of immediate and early loading on bone metabolic activity around dental implants in rat tibiae.
abstract: OBJECTIVE
  The aim of this study was to examine the influence of immediate and early loading on dynamic changes in bone metabolism around dental implants using bone scintigraphy.
  
  
  METHODS
  Two titanium implants were inserted in the right tibiae of 21 rats. Closed coil springs with 4.0-N loads were applied parallel to the upper portion of the implants for 35 days. According to the load application timing, rats were divided into three groups: immediate loading (IL) group, early loading 1 day after implant insertion (1-D early loading [EL]) group, and loading 3 days after implant insertion (3-D EL) group. Rats were intravenously injected with technetium-99 m-methylene diphosphonate (Tc99 m-MDP) (74 MBq/rat) and scanned by bone scintigraphy at 1, 4, 7, 11, 14, 21, 28, and 35 days after load application. The ratio of accumulation of Tc99 m-MDP around the implants to that of a reference site (uptake ratio) was calculated to evaluate bone metabolism.
  
  
  RESULTS
  In every group, the uptake ratio increased until 7 days after load application and then gradually decreased. It was significantly higher than baseline at 4, 7, 11, and 14 days (P < 0.001). The uptake ratio in the 1-D EL and 3-D EL groups were significantly higher than that in the control group and also that in the IL group (P < 0.001).
  
  
  CONCLUSIONS
  Bone metabolism initially increased and then gradually decreased to baseline despite differences in load timing. Increases in bone metabolic activity differed according to load application timing; the later the load application, the more enhanced the bone metabolism.
authors.affiliation: Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Miou
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Toru
authors.initials: T
authors.lastname: Ogawa
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Shigeto
authors.initials: S
authors.lastname: Koyama
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D015921:Dental Implants; D017267:Dental Prosthesis Design; D057893:Immediate Dental Implant Loading; D020007:Implants, Experimental; D008297:Male; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D051381:Rats; D017208:Rats, Wistar; D013669:Technetium Tc 99m Medronate; D013977:Tibia / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000601:surgery*; D014025:Titanium
chemical_list: D015921:Dental Implants; D019275:Radiopharmaceuticals; D014025:Titanium; D013669:Technetium Tc 99m Medronate
keywords: bone metabolic activity; dental implant; early loading; immediate loading; peri-implant bone; rat tibia